Chemical additives for lubricating oils are used to control the physical and chemical properties of the oils. These additives are used to modify oil viscosity and viscosity index, to make the oils more resistant to oxidation, to keep engines and other mechanical equipment clean and protected against corrosion and wear, and keep particulate matter dispersed to minimize or eliminate sludge and deposits.
Hydrocarbon-based chemical additives are designed for specific functions by choosing a hydrocarbon type and molecular weight range or molecular weight distribution to allow the additives to function in the fluid type of interest. For instance, high molecular weight polymers can be used to increase viscosity and viscosity index of mineral oils or synthetic oils. Polar head groups can be designed to be attached to low or high molecular weight hydrocarbon tails to afford detergents, dispersants, antiwear, or anticorrosion agents.
Mannich base dispersants are a class of commercial crankcase dispersants. These compounds are typically produced by reacting alkyl-substituted phenols with aldehydes and amines, such as is described in U.S. Pat. Nos. 3,539,633; 3,697,574; 3,704,308; 3,736,535; 3,736,357; 4,334,085; and 5,433,875. The Mannich products of these inventions are monomeric and limited to relatively low molecular weight and viscosity as dictated by the phenol alkyl substituent's molecular weight. U.S. Pat. No. 5,608,029 details Mannich base polymers via thermal induced ring opening polymerization of cyclic Mannich reaction products of phenols and 1,2 alkylenediamines.
Recent patent disclosures exemplify the utility of polymeric dispersants for improving lube oil compositions. These inventions focus upon the free radical polymerization of olefin containing polymers and unsaturated acidic reactions. U.S. Pat. Nos. 5,112,507 and 5,616,668 detail the use of copolymers of high molecular weight vinylidene containing polymers and unsaturated acidic reactants as useful lube and fuel additives. WO 95/07944 details the polymerization of high molecular weight vinylidene containing polymers, low molecular weight monoethylenically unsaturated compounds, and acidic reactants.
The employment of acylating agents to improve lubricant dispersants is well exemplified in the art. U.S. Pat. No. 4,548,724 discloses that the reaction of polybutenyl succinimides with polycarboxylic acids affords improved dispersancy. U.S. Pat. No. 5,259,968 discloses improved dispersants comprising the reaction products of polyanhydrides and nitrogen or ester containing lubricant adducts. The disclosed polyanhydrides contain at least two anhydride moieties per hydrocarbyl radical joining the anhydride substituents. U.S. Pat. No. 5,464,549 discloses improved dispersants via the reaction of a nitrogen or hydroxy containing dispersant with telechelic compounds substituted with at least two maleic anhydrides or the like. U.S. Pat. No. 4,686,054 discloses the post treatment of succinimide dispersants with maleic or succinic anhydride. U.S. Pat. Nos. 4,509,955 and 4,566,983 disclose a mixture of acylating agents comprised of reaction products of maleic anhydride with both polyolefins of at least 30 carbons derived from C12-30 olefins and polyolefins of at least 30 carbons derived from C2-C8 olefins. U.S. Pat. No. 4,940,552 discloses the passivation of amine containing dispersants toward fluoroelastomers by reaction with dicarboxylic acid or anhydride.
U.S. Pat. Nos. 5,356,550 and 5,719,108 disclose succinimide dispersants obtained from the reaction of a maleic anhydride-olefin copolymer, a succinimide, and a primary or secondary amine. Several recent European Patent Applications disclose improved succinimide compositions utilizing unsaturated acidic reagent-olefin copolymers.
EP 0 776 963 A1 discloses succinimide compositions via alkyl or alkenyl succinic anhydrides, unsaturated acidic-olefin copolymers and polyamines. EP 0 775 740 A2 discloses dispersant/viscosity index improvers via the reaction product of a maleic anhydride-octadecene copolymer (Mn 6,300 to 12,000) and a polyalkyl or alkenyl succinimide and optionally a primary and/or a secondary amine. EP 0 773 234 A1 discloses the dispersant additives generated from the reaction of polyalkyl or alkenyl succinic anhydride, a polyamine, and an oligomer containing a functional group capable of reacting with an amine.
U.S. Pat. No. 5,266,186 discloses an iron sulfide dispersing agent useful to inhibit sludge deposits in refinery processing equipment generated by reaction of a maleic anhydride .alpha.-olefin copolymer with fatty amines. The patent further teaches that effective iron sulfide dispersants are made by reacting succinimides of polybutenyl succinic anhydrides and ethylenediamine with maleic anhydride-.alpha.-olefin copolymers.
U.S. Pat. No. 5,160,349 discloses the reaction products of maleic anhydride-.alpha.-olefin copolymers and heterocyclic compounds as useful antiwear agents in fuels. U.S. Pat. No. 4,391,721 discloses dispersant viscosity index improvers from the reaction of styrene maleic anhydride copolymers and tertiary amino alcohols. U.S. Pat. Nos. 3,933,761; 3,956,149; and 3,959,159 disclose useful lubricant and fuel additives from the reaction of .alpha.-olefin-maleic anhydride copolymers with alcohols and primary or secondary amines containing at least one tertiary amino group or heterocyclic amino group (such as N-alkyl morpholines, N-alkyl imidazoles, etc.).
U.S. Pat. No. 4,873,009 discloses a lube oil dispersant obtained by reacting a C.sub.8 to C.sub.500 polybutene succinic acid or anhydride compound and a hydroxypropoxylated alkylene diamine, the diamine being the reaction product of propylene oxide and an alkylene diamine. This patent also discloses that the dispersant may contain boron at a level that improves the compatibility of the dispersant toward fluorocarbon engine seals.
U.S. Pat. Nos. 5,080,815 discloses a dispersant composition comprising the reaction product obtained by reacting a C.sub.30 to C.sub.250 hydrocarbyl-substituted succinic anhydride with aminoguanidine. U.S. Pat. No. 5,454,962 discloses a dispersing agent made by reacting aminoguanidine with a hydrocarbyl-substituted succinic acid or anhydride in a mole ratio of from about 0.4 to about 1.2 moles of the aminoguanidine per mole of the succinic acid compound.
U.S. Pat. Nos. 5,238,588 and 5,162,086 disclose the incorporation of aromatic amines into maleic anhydride grafted ethylene propylene polymers to afford improved antioxidancy and dispersancy. The aromatic amines react with the succinic anhydride moieties of the grafted polymer.
Multigrade lubricating oils must simultaneously meet both low and high temperature viscometric requirements. The high temperature requirement insures the lubricating oil maintains sufficient protective thickness during engine operation, while the low temperature requirement insures oil pumpability in cold climates. Multigrade lubricating oils are typically designated as follows: SAE 5W30, SAE 10W30, SAE 15W40, etc. The first number in the sequence is associated with the low temperature viscosity requirement as measured by a cold cranking simulator (CCS) at high shear, while the second number is associated with the high temperature viscosity requirement (typically the 100.degree. C. kinematic viscosity). ASTM requirements establish the viscosity limits for specific multigrade oils (e. g. a 5W30 oil requires a -25.degree. C. CCS of .ltoreq.3500 cP and a 100.degree. C. viscosity of 9.5 to 12.4 cSt.)
The dual temperature viscometric requirements for multigrade motor oils presents a major challenge to oil formulators. Formulators utilize viscosity index improvers to address multigrade oil specifications. Conventional viscosity index improvers are oil soluble high molecular weight polymers that afford significant kinematic viscosity increase to base oils. Viscosity index improvers contribute more to the high temperature viscosity of base oils than to the low temperature viscosity of base oils. Solution properties of high molecular weight polymers tend to afford lower viscosities in high shear environments.
The base oils utilized for lubricating compositions have characteristic natural viscosities. While blending base oils of different natural viscosities may meet the high temperature viscosity limits for a multigrade oil, the resulting blend may exceed the required low temperature viscosity. A balance of viscosity index improver and base oil is often employed to achieve a desired multigrade oil.
The balance of base oil and viscosity index improver can present limitations. Incorporation of higher amounts of viscosity index improver into lubricating oils to address high temperature requirements, can result in exceeding the low temperature requirement. While the use of lower natural viscosity base oils can improve the low temperature viscometrics, the lower natural viscosity base oils can result in performance debits. Lower natural viscosity base oils are not as effective in diesel engines and are more prone to volatilization.
The dispersant additives incorporated into lubricating compositions to maintain engine cleanliness and prevent harmful deposits often have an antagonistic effect on the viscometric requirements of multigrade oils. The typical dispersant treat rates required to provide adequate dispersancy increase both the low and high temperature viscosities of base oils. Generally, the dispersants exhibit a more pronounced effect on the low temperature viscosity than on the high temperature viscosity, which can result in an increased low temperature viscosity which exceeds or approaches the required limit.
Formulation of multigrade motor oils becomes increasingly more difficult with this inherent dispersant antagonistic low temperature viscometric effect. A delicate balance of viscosity index improver and increasing proportions of undesirable low natural viscosity base oils is often required to address both the low and high temperature viscometric requirements of motor oils. The polymeric dispersants of the current invention impart excellent blending versatility to lubricating oils. The polymeric dispersants of the current invention afford excellent low temperature viscometrics while permitting the use of advantageous higher natural viscosity base oils. Thus, the polymeric dispersants of the present invention facilitate the formulation of multigrade oils versus conventional dispersants.
The prior art fails to suggest or disclose the novel polymeric Mannich base additives of the present invention which comprise poly(olefin-unsaturated acidic reagents) reacted with Mannich base adducts of alkyl substituted phenols condensed with aldehydes and amines. The materials of this invention are thus an improvement over conventional dispersants because of their effectiveness as dispersants coupled with enhanced blending versatility. The Mannich additives of this invention are distinctive in that they are polymeric rather than monomeric which serves to generate higher molecular weight and higher viscosity Mannich dispersants from conventional starting materials.
The polymeric Mannich additives of the present invention are useful as dispersant additives for oleaginous compositions and impart both superior sludge protection and improved viscometrics to lubricant oils. The polymeric Mannich dispersants of this invention are also essentially chlorine free. The polymeric Mannich dispersant of this invention also exhibit improved compatibility toward fluorocarbon engine seals.